Alkaline oxidation of monoketo monocarboxylic acids



United States Patent ALKALINE OXIDATION OF MONOKETO MONOCARBOXYLIC ACIDS Thomas R. Steadman, Waban, and John 0. H. Peterson, Jr., Medford, Mass, assignors to National Research Corporation, Cambridge, Mass, a corporation of Massachusetts No Drawing. Application July 12, 1955 Serial No. 521,618

Claims. (Cl. 260-537) This invention relates to the production of chemicals and in particular to the production of acids.

A principal object of the present invention is to provide a method for producing dicarboxylic acids from saturated monohydroxy and monoketo monocarboxylic acids.

Another object of the invention is to provide a method for producing acid mixtures comprised essentially of dodecanedioic and undecanedioic acids from l2-hydroxystearic acid and 12-ketostearic acid.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and the order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description.

Heretofore, it was shown in U. S. Patent 2,614,122 that dodecanedioic acid could be prepared by cleaving 12- hydroxystearic acid with an alkali metal hydroxide at elevated temperatures in the presence of a high-boiling saturated petroleum hydrocarbon solvent. Such oxidative cleavage reactions, however, result in a relatively viscous, emulsified mass by reason of the formation of the alkali metal salts of dodecanedioic acid and monocarboxylic acids. This use of a high-boiling petroleum hydrocarbon solvent entails a difiicult separation for the recovery of the monoand dicarboxylic acids. The process of the present invention substantially eliminates the formation of any viscous, emulsified reaction masses and allows the use of a simple procedure for product recovery, with yields of product as high as or higher than can be obtained with the use of a high-boiling petroleum hydrocarbon solvent.

The present invention is directed to the oxidative cleavage of saturated monohydroxy monocarboxylic acids and monoketo monocarboxylic acids to produce a mixture comprised essentially of dicarboxylic acids. This acid mixture comprises a dicarboxylic acid containing the same number of carbon atoms betweenthe carboxyl groups as the number of carbon atoms between the oxygenated functional group (i. e., the hydroxy group or the keto group) and the carboxyl group of the monohydroxy (or -keto) monocarboxylic acid starting material and a dicarboxylic acid containing one less carbon atom than the first mentioned dicarboxylic acid.

The process of the present invention is preferably achieved by cleaving a saturated monohydroxy monocarboxylic acid whose hydroxyl group is attached to a nonterminal secondary carbon atom or a saturated monoketo monocarboxylic acid with an alkali metal hydroxide at a temperature between about 300 C. and 375 C. in the presence of a solvent comprising water. In one preferred embodiment of the invention, the saturated monohydroxyl and monoketo monocarboxylic acids are l2-hydroxystearic acid and l2-ketostearic acid respectively, and the dicarboxylic acids produced therefrom are dodecanedioic and undecanedioic acids. Another Pl'efferred embodiment of the invention calls for the reaction to be carried out inthe presence of a material selected from the group consisting of cadmium oxide and zinc oxide. The long chain dicarboxylic acids'dodecanedioic and undecanedioic acids, produced by the present invention, and their derivatives have considerable utility. For instance, they may be used as. components of synthetic lubricants, viscosity index improvers, pour point: depressants and petroleum lubricants. The acids also pro; vide valuable chemical intermediates for the manufac: ture of resins such as polyesters and the like. Likewise, some of the esters of these acids may be used as plasticizers, particularly for polyvinyl compounds, such as is shown in the copending application of Steadman et'al Serial No. 521,617, filed on even date herewith, .'-and now abandoned.

Specific detailed methods of practicing thepresent amples.

Example I grams of IZ-hydroxystearic acid, 32gram s ofsodiu hydroxide, 99 grams of water, and-3.'0 grams of cadmium oxide were charged to a high-pressure reactor; The reactor was then sealed and the reaction mixture was brought up to operating temperature within" the range of 325 C. to 330 C. During the reaction-the pressure in the sealed reactor rose from about 15 p.-'s.i.' to about 2000 p. s. i. After 14 hours the reaction was terminated and the aqueous solution containing the sodium salts of dodecanedioic and undecanedioic'acidsand monobasic acids was steam distilled to remove the low-boiling organic material. The resulting aqueous solution was acidified with a slight excess of mineral acid to precipitate the crude acids which were removed from the mixture by filtration and then steam distilled to remove the monocarboxylic acids. The dicarboxylic acid mixture was recovered and recrystallized'from toluene. In thisway, there was obtained 21.3 grams of a mixture of C and C dicarboxylic acids with an equivalent weight of 122.5. A yield of 40.8% based on the 12-hydroxys'tearicacid was thus obtained.

Example II Example III This reaction was carried outas in Examplel (under approximately the same conditions of temperature, charge, solvent, etc.) except that zinc oxide wasv em ployed instead of cadmium oxide and the-reaction was terminated after only 5 hours duration. This run .pro-

duced 15.6 grams of a mixture of dode canedioic and nndecanedioic acids. A yield of 29.8% based on the 12-hydroxystearic acid was thus obtained.

Example IV This reaction was carired out as in Example I (under approximately the same conditions of temperature, charge, solvent, etc.) except that 65 grams of cadmium oxide were initially charged to the reactor. The mixture of crude acids recovered in this run was subjected to 3 analysis by partition chromotography. It was shown that the acid mixture consisted of 6.3 grams of dodecanedioic acid, 20.3 grams of undecanedioic acid, a very small amount oftridecanedioic acid and palmitic acid. The dicarboxylic acids recovered represented a yield of 51.1% based on the 12-hydroxystearic acid.

While specific examples of the present invention have been given above, they are subject to wide variations Without departing from the scope thereof. "For instance, although only 12-hydroxystearic acid and 12-ketostearic acid were illustrated, other saturated monohydroxy and monoketo monocarboxylic acids and derivatives thereof can be employed in the present process. Hydroxystearic acids such as IO-hydroxystearic acid, 14-hydroxystearic acidiand the like and the corresponding ketostearic acids are particularly well suited for use in the present process. The oxidative cleavage is also preferably carried out in'a solvent. This solvent, preferably water, dissolves the alkali salts of themono and dicarboxylic acids as they areformed and thus prevents the reaction mass from becoming too viscous due to the precipitation of the alkali acid salts. By maintaining the reaction mixture fluid, amore efficient reaction is achieved. Also, since the alkali salts of the mono and dicarboxylic acids are dissolved in the water at the termination of the reaction, the desired'products can be more readily separated from other reaction products. The quantity of water employed in the reaction may vary considerably. However, it is preferable to employ an amount of water as solvent which is at least equal to or greater than twice (by weight) the charge of alkali metal hydroxide. In the examples,'the quantity of water employed was about three times the charge of the sodium hydroxide.

In. one embodiment of .the invention, it is preferable to employ a material selected from the group consisting of cadmiumaoxide and zinc oxide. Cadmium or zinc oxide may be added as such to the reaction, or the desired oxide may be formed therein by employing a zinc or cadmium icompound (e. g., zinc acetate) which is readily reducible to the oxide in an alkaline medium. The terms cadmium oxide and zinc oxide as used herein are meant to embody both concepts. The use of these materials has been found to substantially reduce competing side reactions and thus increase the yields of the desired dicarboxylic acids. The quantities of the preferred cadmium oxide and zinc oxide employedin the reaction maybe varied considerably. For instance, in Example-I only a catalytic amount of'cadmium oxide was employed, Whereas inExample IV an amount equal to the stoichiometric quantity capable of reacting with the hydrogen produced by the reaction was employed. However, for the highest yields, it 'is preferable to carry out the reaction in the presence of a stoichiometric amount ofcadmium oxide or zinc oxide capable of reacting with the hydrogen produced during the reaction. For this purpose, the Oxides of cadmium or zinc serve as hydrogen.

acceptors. v

1 The oxidative cleavage is achieved by means of an alkali metal hydroxide. It has been found preferable to employ either sodium hydroxide or potassium hydroxide in excess of the quantity required for the reaction.

The range of operating temperatures and reaction times can be varied within considerable limits. The temperatures may be varied between, about 300 C. and 375 C. The time of reaction may be varied so that, for example, somewhat shorter periods than those given in the examples are satisfactory.

Since certain changes may be made in the above process without departing from the scope of the invention herein involved, it is intended that all matter contained 4 in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A process for preparing dicarboxylic acids from a stearic acid containing only a single keto group which comprises reacting said acid with an alkali metal hydroxide in the presence of water and a'material selected from the group consisting of cadmium oxide and zinc oxide at a temperature between about 300 C. and 375 C., the quantity of water present being at least twice by weight the quantity of alkali metal hydroxide employed, acidifying the resultant aqueous solution, and recovering an acid mixture comprised essentially of a dicarboxylic acid containing the same number of carbon atoms between the carboxyl groups as the number of carbon atoms between the keto group and thecarboxyl group of said monoketo stearic acid and a second dicarboxylic acid containing one less carbon atom than said first mentioned dicarboxylic acid.

2. Process of claim'l wherein said monoketo stearic acid is 12-ketostearic acid and the dicarboxylic acids are dodecanedioic and undecanedioic acids.

3. A process for preparing dicarboxylic acids from a stearic acid containing only a single hydroxy group in which the hydroxyl group is attached to a non-terminal secondary carbon atom which comprises reacting said acid with an alkali metal hydroxide in the presence of Water and a material selected from the group consisting of cadmium oxide and zinc oxide at a temperature between about 300 C. and 375 C., the quantity of water present being at least twice by weight the quantity of alkali metal hydroxide employed, acidifying the resultant aqueous solution, and recovering an acid mixture comprised essentially of a dicarboxylic acid containing the same number of carbon atoms between the carboxyl groups as the number of carbon atoms between the hydroxy group and the carboxyl group of said monohydroxy stearic acid and a second dicarboxylic acid con: taining one less carbon atom than said first mentioned dicarboxylic acid.

4. Process of claim 3 wherein said monohydroxy stearic acid is 12-hydroxystearic acid and the dicarboxylic acids are dodecanedioic and undecanedioic acids.

5. A process for preparing alkali metal salts of dicarboxylic acids from ascompound selected from the group consisting of stearic acids containing only a single keto group and stearic acids containing only a single hydroxy group which comprises reacting said compound with an alkali metal hydroxide in the presence of water at a temperature between about 300 C. and 375 C., the quantity of'water' present being at least twice by weight the quantity of alkali metal hydroxide employed, and recovering the alkali metal salts of a dicarboxylic acid containing the-same number of carbon atoms between the carboxyl groups as the number of carbon atoms between the oxygenated functional group and the carboxyl group of said compound and a second dicarboxylic acid containing one less carbon atom than said first'mentioned dicarboxylic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,182,056 Bruson Dec. 5, 1939 2,323,061 Lehmann June 29, 1943 2,614,122 Mikeska Oct. 14, 1952 2,696,501 Stein Dec. 7, 1954 2,766,267 Hill Dec. 9, 1956 2,777,865 Logan Jan. 15, 1957 

1. A PROCESS FOR PREPARING DICARBOXYLIC ACIDS FROM A STEARIC ACID CONTAINING ONLY A SINGLE KETO GROUP WHICH COMPRISES REACTING SAID ACID WITH AN ALKALI METAL HYDROXIDE IN THE PRESENCE OF WATER AND A MATERIAL SELECTED FROM THE GROUP CONSISTING OF CADMIUM OXIDE AND ZINC OXIDE AT A TEMPERATURE BETWEEN ABOUT 300*C. AND 375* C., THE QUANTITY OF WATER PRESENT BEING AT LEAST TWICE BY WEIGHT THE QUANTITY OF ALKALI METAL HYDROXIDE EMPLOYED, ACIDIFYING THE RESULTANT SOLUTION, AND RECOVERING AN ACID MIXTURE COMPRISED ESSENTIALLY OF A DICARBOXYLIC ACID CONTAINING THE SAME NUMBER OF CARBON ATOMS BETWEEN THE CARBOXYL GROUPS AS THE NUMBER OF CARBON ATOMS BETWEEN THE KETO GROUP AND THE CARBOXYL GROUP OF SAID MONOKETO STEARIC ACID AND A SECOND DICARBOXYLIC ACID CONTAINING ONE LESS CARBON ATOM THAN SAID FIRST MENTIONED DICARBOXYLIC ACID. 